Many Cannabis genetics naturally grow tall, with a similar appearance to pine trees, with one large bud on top and a smaller cola on the end of each branch. This growing method is successful outdoors because the sun moves across the sky throughout the day, allowing each branch (and bud) to receive light. However, when growing indoors, and to a lesser extent in greenhouses, this does not happen because the lights are stationary above the plants, never fully lighting the sides. Additionally, when growing indoors, it is important to keep the plant canopy as even as possible due to diminishing light intensity as the flowers get further from the light source (see: Inverse Square Law); this is not a problem with sun-grown cannabis as the sun is so far away that a few extra feet doesn’t make as much of a difference.

Lighting is a huge part of commercial cannabis cultivation. Some estimates assign up to 33% of all energy used in an indoor grow to lighting. Additionally, the number of lights you plan to use will determine the size of your grow (commercial grows are often referred to by the number of lights they include, rather than by square footage).